Sliding pool mercury switch



June 10, 1958 E. N. OELAND, JR 2,838,632

' SLIDING Poor. MERCURY SWITCH Filed June 21, 1956 i 5ay y g2 63 54 4/ n 61 if 66 ff! Y 59 56 59 6.ov 4i f-Ji' i INVENTQR. g [zA/57M 05m/WJ: 2 i ,I .i 4; BY d.: QZ

United States atent iitice 2,838,632 SLIDING POOL MERCURY SWITCH Ernest N. Deland, Jr., West Covina, Calif. Application June 21, 1956, Serial No. 592,765 3 Claims. (Cl. 20G-112) This invention relates generally to mercury switches, and more particularly to a mercury switch in which a pair of relatively slidable members of non-conducting material move one or more pools of mercury into electrical contact at the sliding surfaces, and are resiliently urged together at their sliding faces by spring means to provide for expansion, wear, and pool-sealing contact. ln its preferred form, the switch is a hermetically sealed relay with relatively rotatable sliding members mounted on a common axis and resiliently urged into contact in a longitudinal direction.

In guided missiles and jet aircraft, a great many switches are required as parts of the complex electronic and electric systems used for steering, fire-control, navigation, etc. Speed and other performance requirements for these aircraft have been rapidly increasing in recent years, with the consequence that switches heretofore known are mostly. unreliable or entirely inoperative or too heavy if used in advanced designs. Every component in these designs must function satisfactorily in the presence of powerful accelerational forces, whichmay come from any direction and which change direction many times during flight. The entire aircraft may be subjected to severe shocks during take-off or firing, or as a result of weather or combat conditions. Vibration is almost impossible to eliminate entirely, and any unusual er1- vironmental condition or minor damage may increase it to violent proportions.

It is not sufficient merely to use larger and stronger switches of conventional design. On the contrary, smaller and lighterswitches are required. In addition to reduction in size and weight, specifications usually call for reduced impedance, in order to `detect weak signals; low inertia to permit operation with minimum work; reliable operation over a temperature range extending from well below freezing to about 200 F.; and ability to with stand a certain amount of arcng and other defective performance without diminishment in performance.

Mercury switches have hitherto been practicaliy unused in the applications above described because they depend on gravity for their operation. Conventional mercury switches, though light in weight, low in impedance, and reliable in performance on earthbound equipment, could not be used in aircraft because the shaking they would get would splash the mercury pool into contact, or break contact when it was most neededwhen the aircraft was in violent maneuver.

In the past, it has been considered impractical to use a mercury pool entirely filling a cavity in an insulating bodyas a switch contact. The best insulating materials were breakable. Other known insulating materials, suchasplastics, were distrusted because they became unreliable in operation as their sliding surfaces became worn, or after arcing produced in them a trail of low resistance residue or ash which made future arcing more likely.

In spite of these problems, the hunt for a shock-proof and shake-proof mercury switch for use in aircraft has 2,838,632 Patented June 10, 1958 2 commanded considerable research time in expense because of the many virtues inherent in mercury switches. Some rather large and clumsy laboratory models have been produced, but they have generally failed after a few hundred cycles of operation, or have involved so much bulk, weight, and inertia as to be unsatisfactory in aircraft or in any device requiring rapid and easy action.

it is a major object of the present invention to provide a mercury switch which is shockproof and unaffected in operation by shaking or acceleration in any direction.

It is another major object to provide a mercury switch which is sufficiently resilient in construction to allow for expansion and wear.

Another important object is to provide a mercury switch in which arcing `does not produce a low resistance path.

A further object is to provide a mercury switch which is a mechanically sliding type, but which is proof against wear or leakage for thousands of operations and may be hermetically sealed in a housing because of low servicing requirements.

A still further object is to provide a mercury switch of the sliding pool type with a minimum weight, volume` and inertia.

The foregoing and other objects are accomplished by means of a pair of relatively slidable members of nonconducting material, at least one of which carries a mercury pool exposed to the sliding surface of the other. The latter surface is provided with some electrical contact means, preferably, but not necessarily, another -mercury pool. In one species described herein, one member is merely a relatively thin plate of non-conducting material provided with openings at appropriate points.

Preferably, the two members are mounted on a common axis and one is rotatable relative to the other.

The mercury substantially fills the containing cavity, residual space, if any, being too small to allowenough splashing or pool movement to interfere with the action of the switch.

The adjacent contacting surfaces are preferably but not necessarily plane.

Other features of the invention, some optional and some essential, will be presented in the course of the following description of two specific embodiments, which are illustrated in the accompanying drawings, in which:

Figure 1 is a longitudinal sectional view of a hermetically sealed, solenoid operated, rotary action mercury relay constructed according to my invention;

Figure 2 is an exploded perspective View of the principal switch members, one being partially broken away to reveal its interior;

Figure 3 is a bottom view Figure l; and

Figure 4 is a vlongitudinal sectional view of another rotary relay species of the invention.

In Figure 1, the numeral 10 indicates the relay generally. A switch assembly, indicated generally by the numeral 11, and a rotary operating solenoid, indicated generally by the numeral 12, are carried on a mounting sleeve 13, which is in turn supported on a base 14. A housing 15 of tubular shell shape screws on the base 14 at threads 16, to enclose the working parts of the relay.

Although the base 14 is provided with a plurality of openings 17 for electrical conduits to the solenoid 12 and the switch assembly 11 (see the view of the base in Figure 3), glass or plastic seals 18 till these openings around the leads when assembly is completed so that the entire relay 10 is hermetically sealed and its housing 15 can be filled with hydrogen, nitrogen, or other non-oxidizing, arc-quenching gas, through one of the openings 17 after assembly by methods well known to those skilled in the glass tube art.

of the relay illustrated in The mounting sleeve 13 is a piece of tubing fixed in thefhase 14 and closed at its upper end by a cover 19. The lower end of the mounting sleeve is provided with a number of lateral openings 20, through which wiring may pass from the base opening 17 to the switch assembly 1l, as illustrated by the electrical conductor 2l.

The sleeve 13 and the switch assembly 11 are sulficiently smaller in diameter than the inside diameter of housing so that the latter can be readily assembled over the wiring in the annular space around the assembly.

The rotary solenoid 12 may be any electrically op- -erated relay means but is preferably a rotary solenoid having a coil 22 and an armature 23, which is moved upward toward solenoid 22 when the latter is supplied with current. A coil spring 24, seen only in section, holds the armature 23 in a withdrawn (downward position) when no current is flowing in the coil 22.

A centrallyY positioned shaft 25, rotatably mounted in a ball bearing 26 in cover 19 and a bearing 27 in the bottom of solenoid 1.2, is adapted to be rotated 45 by a cam arrangement to be described when the solenoid 12 is operated, remaining in the rotated position until the coil 22, is tie-energized, at which time it is rotated in a reverse. direction to its original position by a flat clock 2" spring 28, which is attached to the lower end 29 of the shaft 25, and to the solenoid 12.

A non-rotating plunger sleeve 38, encircling shaft 25, is carried on the armature. At its upper end, the plunger sleeve 30 is provided with a notched cam 3i having a guide wall 32 engaging a cam roller 33 carried on the shaft 25 and shaped to rotate the shaft 25 the required 45 when the cam 31 moves longitudinally upward.

The principal parts of the switch assembly 11 are the three members mounted on the upper part of shaft 25 and indicated by the numeral 11a in Figure 2. The lowermost of these, which may be identified as the terminal pool member 34, is stationary, being pinned byl pins 35 to the cover 19 and the solenoid 12. The uppertwo members, which may be identified as the pressure pool member 36 and the spring member 37 rotate with the shaft 25 by virtue of a transverse pin 38V through the spring member 37 and the upper end of the shaft 25, and four pins 39 which integrate the pressure. pool member 36 rotationally with the spring member 37, being received in holes 39a in the upper surface of the pressure plate member 36.

Each of the four pins 39 is encircled by a small helical spring 4Q, the four springs 49 serving to resiliently urge the rotatable pressure pool member 36 into contact with i the stationary terminal pool member 34 at the transverse plane of contact of their adjacent surfaces 41 and 42.

The terminal pool member 34 and the pressure pool member 36 are recessed in their adjacent surfaces 41 and 42 with a plurality of recesses, preferably of sectorshaped transverse cross section, disposed about the axis ofI rotation. In the illustrated embodiment, there are eight terminal recesses 43 in the surface 4l of the terminal pool member 34 and four pressure pool recesses 44 in the surface 42 of the pressure pool member 36. Each of the recesses 43 and 44 is substantially filled with a pool of mercury 45 or 45a, respectively, as indicated in the cross-sectional view of Figure l. Y

A brass terminal 46, with a partially threaded shank, is received through threaded opening 47 in the wall of the terminal pool member 34, placing lead 2l in communication with the mercury pool 45. Each of the mercury pools 45 is similarly provided with a terminal 46.

Each of the pools 45 inthe terminal pool member 34. may be connected to an external circuit by means of a lead such as the conductor 21, which reaches the exterior by way of the lateral opening Ztlin the mounting sleeve'13 and the base opening i7. Complete wiring has not been added since it. forms no distinguishing or 4 novel part of the relay rand would only obscure the drawing.

The pools 45a in the pressure pool member 36 may be likewise provided with leads to an external circuit, to provide eight circuit connections, four in the unrotated position of the rotary solenoid 12, and four in the rotated position. However, this involves a certain amount of lead exing for the leads to the rotatable pressure pool member 36. If maximum reliability is required, it is preferred that the four pools 45a be connected in pairs with conductors which experience no flexing since they merely ride with the pressure pool member 36. The relay then provides four circuit connections, two in one position and two in the other.

I have found that a fluorocarbon plastic such as those sold commercially as Teflon or Kel-F has unique advantages as material for the pool-carrying members, although other halocarbon plastics may be used, and even ordinary insulating materials may be used where breakage or arc break-down are not problems. Even in these instances, however, it is important that the members have surfaces which are readily slidable when urged into pool-,sealing contact. t

In the preferred form of the invention, it is important to use an. insulating material for the pool-carrying members which leaves no path of lowered resistance after being exposed to arcing. Such materials, the above-mentioned fluorocarbon plastics being the preferred examples, merely vaporize upon exposure to arcing and do not produce any solid ash of degenerated material to serve as a pathV of lowered resistance which might produce future arcing. Such materials may be referred to as ashless In Figure 4, anotherY species of the invention is illustrated. Many parts correspond to similar parts in the species of Figure l, and where identical, are identified by the same numeral with a prime signV added. Thus the base 14', the housing 15, and the solenoid 12 remain unchanged in form and function. The mounting sleeve 48 is very similar to the Vsleeve 13, but is provided with g pool member 51. The pressure pool member 52 and the spring member 53 are like the corresponding parts 36 and 37 of the species of Figure l, but they do not rotate, since the shaft does not rotate. The springs 54 urge the pressure pool member 52 longitudinally with respect to shaft 50 toward the terminal pool member 51, but these two members have interposed between them a third insulating member, a relatively thin, disc-shaped switch member 55, which is rotatable on the shaft 50 by the solenoid 12 by means of a crank armV 56, which extends through the slot 49 and engages a small lever 57 projecting from one edge of the switch member 55.

The terminal pool member 51 has a plurality of sector-cross-section recesses 5S, filled with mercury pools 59, in its upper surface 60, and the pressure pool member 52 is similarly provided with mating recesses 61, filled with mercury pools 62, and its lower surface 63. Terminals 64 and 65 communicate with the recesses 5S and 61, respectively, and may be connected as desired to each other or to an exterior circuit as in the case of the species of Figure l.

The switch member is provided with a number of openings 66 which correspond in shape and location to the recesses 5S and 61, so that the pools 59 and 62 in these recesses may be placed in or out of electrical contact with each other, as desired, by the rotation ot the switch member 55 through 45 by the solenoid 12. The openings 66 may or may not carry their own mercury pools from one switch position to another. This will depend upon the relationship between the thickness of the switch member 55 and the surface tension of mercury.

5 It is preferred, however, that the switch member S5 have suilcient thickness to carry with it its own mercury pools.

It will be understood that the specific embodiments of the foregoing description are not limited to the particular number, shape, or arrangement of recesses shown. The angle of rotation may be more or less than 45 and the reciprocating solenoid described bereplaced by other electrical or non-electrical means, or even manual control. The rotating means may progress always in the same direction of rotation instead of returning to the same starting point.

Furthermore, the embodiments described are illustrative of my invention only, and it is not my intention to present them as the only forms which my invention may take. On the contrary, the scope of my invention includes not only the embodiments described and their preferred forms, but all switches, relays, and devicesfalling within the scope of the appended claims.

I claim:

l. A mercury switch which includes: a housing filled cal conduits communicating between at least some of said pools and the exterior of said housing; and spring means resiliently urging said members into contact.

2. A shock-proof hermetically sealed mercury relay which includes: a hermetically sealed housing filled with arc-quenching gas; rotary solenoid means mounted in said housing and including a shaft rotatable by said solenoid and electrical leads communicating with the exterior of said housing; a terminal pool member and a pressure pool member mounted on said shaft and longitudinally slidable thereon, one of said members being rotatable relative to the other by the action of said shaft; spring means resiliently urging said members into contact at their adjacent surfaces; mating mercury pools carried in recesses in the contacting surfaces of said members and adapted to slide into or out of contact with each other by the rotation of said shaft; and electrical leads from at least some of said pools to the exterior of said housing. 3. A shock-proof hermetically sealed mercury relay which includes: a hermetically sealed housing filled with arc-quenching gas; rotary solenoid means mounted in said housing and including a shaft rotatable by said solenoid and electrical leads communicating with the exterior of said housing; a terminal pool member and a pressure pool member of ashless fluorocarbon mounted on said shaft with flat adjacent surfaces and longitudinally slidable thereon, said pressure pool members being rotatable relative to said terminal pool member by the action of said shaft; spring means resiliently urging said members into contact at their adjacent surfaces; walls defining mating recesses of sector-shaped cross section disposed about the axis of said shaft in the contacting surfaces of said members; mercury pools substantially filling said recesses; electrical conducts interconnecting a plurality of said pools in said pressure pool member; and electrical leads from said pools in said terminal pool member communicating with the exterior of said housing.

References Cited in the le of this patent UNTTED STATES PATENTS 382,845 Tesla May l5, 1888 1,668,161 Long May 1, 1928 1,983,150 Sigman Dec. 4, 1934 2,606,256 Sissenwine et al Aug. 5, 1952 

